A randomized, double-blind, placebo-controlled trial of aldafermin in patients with NASH and compensated cirrhosis.

BACKGROUND AND AIMS: Aldafermin, an engineered analog of the human hormone FGF19, improves liver histology in patients with noncirrhotic NASH; however, its efficacy and safety in compensated cirrhosis is unknown. No drug has yet to demonstrate benefit in the compensated NASH population. APPROACH AND RESULTS: In this multicenter, double-blind, placebo-controlled, phase 2b trial, 160 patients with compensated NASH cirrhosis were randomized to aldafermin 0.3 mg (n = 7), 1 mg (n = 42), 3 mg (n = 55), or placebo (n = 56) for 48 weeks. The 0.3 mg group was discontinued to limit exposure to suboptimal doses. The primary end point was a change in Enhanced Liver Fibrosis from baseline to week 48. The analyses were performed in the intention-to-treat population. At week 48, the least-squares mean difference in the change in Enhanced Liver Fibrosis was -0.5 (95% CI, -0.7 to -0.2; p = 0.0003) between the 3 mg group and the placebo group. 15%, 21%, and 23% of patients in the placebo, 1 mg, and 3 mg group, respectively, achieved fibrosis improvement ≥ 1 stage; and 13%, 16%, and 20% achieved fibrosis improvement ≥ 1 stage without NASH worsening. Improvement in alanine aminotransferase, aspartate aminotransferase, neoepitope-specific N-terminal pro-peptide of type III collagen, and liver stiffness favored aldefermin groups over placebo. Diarrhea was the most frequent adverse event, occurring at 26% and 40% in the 1 mg and 3 mg groups, respectively, compared to 18% in the placebo group. Overall, 0%, 2%, and 9% of patients in the placebo, 1 mg, and 3 mg group, respectively, discontinued due to treatment-related adverse events. CONCLUSIONS: Aldafermin 3 mg resulted in a significant reduction in Enhanced Liver Fibrosis in patients with compensated NASH cirrhosis.

Aldafermin in patients with non-alcoholic steatohepatitis (ALPINE 2/3): a randomised, double-blind, placebo-controlled, phase 2b trial.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis, inflammation, and injury, and is associated with an increased risk of liver transplantation and death. NASH affects more than 16 million people in the USA, and there is no approved therapy. The aim of this study was to evaluate the safety and efficacy of aldafermin, an engineered analogue of the gut hormone fibroblast growth factor 19 (FGF19). METHODS: In this randomised, double-blind, placebo-controlled, phase 2b study (ALPINE 2/3) in patients with biopsy-confirmed NASH and stage 2 or 3 fibrosis, we randomly assigned patients stratified by fibrosis stage in a 1:1:1:1 ratio to receive placebo, aldafermin 0·3 mg, 1·0 mg, or 3·0 mg once daily for 24 weeks at 30 study sites in the USA. Patients, investigators, the funder, and all other staff, were masked to treatment assignment throughout the study. The primary endpoint was an improvement in liver fibrosis of at least one stage with no worsening of NASH at week 24. Analyses were done by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT03912532, and has been completed. FINDINGS: Between May 16, 2019, and Sept 4, 2020, 786 patients were screened, of whom 171 were randomly assigned to a treatment group and included in the intention-to-treat population: 43 in the 0·3 mg aldafermin group, 42 in the 1·0 mg group, 43 in the 3·0 mg group, and 43 in the placebo group. In total, 145 (85%) of patients completed treatment. At week 24, among patients with biopsies at both baseline and week 24, was seven (19%) of 36 patients in the placebo group, 11 (31%) of 36 in the 0·3 mg aldafermin group (difference 90% CI 12% [-9 to 33]; p=0·11), five (15%) of 34 patients in the 1·0 mg group (difference -5% [-24 to 13]; p=0·80), and 11 (30%) of 37 patients in the 3·0 mg group (difference 10% [-9 to 30]; p=0·12) had an improvement in liver fibrosis of at least one stage with no worsening of NASH, without meeting the prespecified significance for dose response (p=0·55). Adverse events were mostly mild or moderate in severity. Diarrhoea occurred in six (14%) of 43 patients in the placebo group, three (7%) of 43 patients in the 0·3 mg aldafermin group, five (12%) of 41 patients in the 1·0 mg group, and ten (23%) of 43 patients in the 3·0 mg group. Incidences of serious adverse events and discontinuations owing to adverse events were similar between groups. INTERPRETATION: Aldafermin was generally well tolerated but did not produce a significant dose response on fibrosis improvement of at least one stage with no worsening of NASH, despite positive effects on a number of secondary endpoints. The findings of this trial may have implications for the design of future NASH trials. FUNDING: NGM Biopharmaceuticals.

Potent suppression of hydrophobic bile acids by aldafermin, an FGF19 analogue, across metabolic and cholestatic liver diseases.

BACKGROUND & AIMS: Higher serum bile acid levels are associated with an increased risk of cirrhosis and liver-related morbidity and mortality. Herein, we report secondary analyses of aldafermin, an engineered analogue of the gut hormone fibroblast growth factor 19, on the circulating bile acid profile in prospective, phase II studies in patients with metabolic or cholestatic liver disease. METHODS: One hundred and seventy-six patients with biopsy-confirmed non-alcoholic steatohepatitis (NASH) and fibrosis and elevated liver fat content (≥8% by magnetic resonance imaging-proton density fat fraction) received 0.3 mg (n = 23), 1 mg (n = 49), 3 mg (n = 49), 6 mg (n = 28) aldafermin or placebo (n = 27) for 12 weeks. Sixty-two patients with primary sclerosing cholangitis (PSC) and elevated alkaline phosphatase (>1.5× upper limit of normal) received 1 mg (n = 21), 3 mg (n = 21) aldafermin or placebo (n = 20) for 12 weeks. Serum samples were collected on day 1 and week 12 for determination of bile acid profile and neoepitope-specific N-terminal pro-peptide of type III collagen (Pro-C3), a direct measure of fibrogenesis. RESULTS: Treatment with aldafermin resulted in significant dose-dependent reductions in serum bile acids. In particular, bile acids with higher hydrophobicity indices, such as deoxycholic acid, lithocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, and glycocholic acid, were markedly lowered by aldafermin in both NASH and PSC populations. Moreover, aldafermin predominantly suppressed the glycine-conjugated bile acids, rather than the taurine-conjugated bile acids. Changes in levels of bile acids correlated with changes in the novel fibrogenesis marker Pro-C3, which detects a neo-epitope of the type III collagen during its formation, in the pooled NASH and PSC populations. CONCLUSIONS: Aldafermin markedly reduced major hydrophobic bile acids that have greater detergent activity and cytotoxicity. Our data provide evidence that bile acids may contribute to sustaining a pro-fibrogenic microenvironment in the liver across metabolic and cholestatic liver diseases. LAY SUMMARY: Aldafermin is an analogue of a gut hormone, which is in development as a treatment for patients with chronic liver disease. Herein, we show that aldafermin can potently and robustly suppress the toxic, hydrophobic bile acids irrespective of disease aetiology. The therapeutic strategy utilising aldafermin may be broadly applicable to other chronic gastrointestinal and liver disorders. CLINICAL TRIALS REGISTRATION: The study is registered at Clinicaltrials.govNCT02443116 and NCT02704364.

Efficacy and Safety of Aldafermin, an Engineered FGF19 Analog, in a Randomized, Double-Blind, Placebo-Controlled Trial of Patients With Nonalcoholic Steatohepatitis.

BACKGROUND & AIMS: Aldafermin, an engineered analog of fibroblast growth factor 19, inhibits bile acid synthesis and regulates metabolic homeostasis. We report results from a 24-week, phase 2 study, with serial liver biopsies, of patients with nonalcoholic steatohepatitis (NASH). METHODS: We performed a double-blind study of 78 patients with NASH at 9 centers in the United States. Key inclusion criteria were biopsy-proven NASH with Nonalcoholic Fatty Liver Disease Activity Score ≥4, stage 2 or 3 fibrosis by NASH Clinical Research Network classification, and absolute liver fat content ≥8%, measured by magnetic resonance imaging-proton density fat fraction. Patients were randomly assigned (1:2) to groups given subcutaneous placebo (n = 25) or aldafermin 1 mg (n = 53) daily for 24 weeks. The primary outcome was change in absolute liver fat content from baseline at week 24. Secondary outcomes included serum markers and histologic measures of fibrosis improvement and NASH resolution. RESULTS: At week 24, the aldafermin group had a significant reduction in absolute liver fat content (reduction of 7.7%) compared with placebo (reduction of 2.7%; difference, reduction of 5.0%; 95% confidence interval, reduction of 8.0%-1.9%; P = .002). Aldafermin produced significantly greater decreases in levels of 7α-hydroxy-4-cholesten-3-one, bile acids, alanine and aspartate aminotransferases, and neoepitope-specific N-terminal pro-peptide of type III collagen (Pro-C3) than placebo. Fibrosis improvement (≥1 stage) with no worsening of NASH was achieved in 38% of patients receiving aldafermin vs 18% of patients receiving placebo (P = .10). NASH resolution with no worsening of fibrosis was observed in 24% of patients given aldafermin vs 9% of patients given placebo (P = .20). Discontinuations due to adverse events occurred in no patients in the aldafermin group and 4% of patients in the placebo group. CONCLUSIONS: In a phase 2 trial of patients with NASH, aldafermin reduced liver fat and produced a trend toward fibrosis improvement. ClinicalTrials.gov, Number: NCT02443116.

The Commensal Microbe Veillonella as a Marker for Response to an FGF19 Analog in NASH.

BACKGROUND AND AIMS: The composition of the human gut microbiota is linked to health and disease, and knowledge of the impact of therapeutics on the microbiota is essential to decipher their biological roles and to gain new mechanistic insights. Here we report the effect of aldafermin, an analog of the gut hormone FGF19, versus placebo on the gut microbiota in a prospective, phase 2 study in patients with NASH. APPROACH AND RESULTS: A total of 176 patients with biopsy-confirmed nonalcoholic steatohepatitis (NASH) (nonalcoholic fatty liver disease activity score ≥ 4), fibrosis (F1-F3 by NASH Clinical Research Network criteria), and elevated liver fat content (≥ 8% by magnetic resonance imaging-proton density fat fraction) received 0.3 mg (n = 23), 1 mg (n = 49), 3 mg (n = 49), and 6 mg (n = 28) aldafermin or placebo (n = 27) for 12 weeks. Stool samples were collected on day 1 and week 12 and profiled using 16S ribosomal RNA gene sequencing; 122 patients had paired stool microbiome profiles at both day 1 and week 12. Overall, the state of the gut microbial community was distinctly stable in patients treated with aldafermin, with all major phyla and genera unaltered during therapy. Patients treated with aldafermin showed a significant, dose-dependent enrichment in the rare genus Veillonella, a commensal microbe known to have lactate-degrading and performance-enhancing properties, which correlated with changes in serum bile acid profile. CONCLUSIONS: Veillonella may be a bile acid-sensitive bacteria whose enrichment is enabled by aldafermin-mediated suppression of bile acid synthesis and, in particular, decreases in toxic bile acids. This study provides an integrated analysis of gut microbiome, serum bile acid metabolome, imaging, and histological measurements in clinical trials testing aldafermin for NASH. Our results provide a better understanding of the intricacies of microbiome-host interactions (clinicaltrials.gov trial No. NCT02443116).

Comparative resource utilization and costs for patients with acute coronary syndrome managed with percutaneous coronary intervention and treated with clopidogrel or prasugrel.

PURPOSE: Results of a study of bleeding events and other inhospital outcomes with the use of clopidogrel versus prasugrel in patients with acute coronary syndrome (ACS) managed with percutaneous coronary intervention (PCI) are reported. METHODS: Demographic and clinical data on adults hospitalized for ACS, managed with PCI, and treated with clopidogrel or prasugrel during a two-year period were extracted from a large hospital claims database. Bleeding rates, hospital length of stay (LOS), and total hospital costs during the index hospitalization were evaluated. RESULTS: The study sample consisted of 75,297 patients who received clopidogrel and 9,477 who received prasugrel. The unadjusted bleeding rates were 5.7% with clopidogrel use and 3.2% with prasugrel use (p < 0.0001). After propensity score stratification to adjust for selection bias, rates of bleeding events were not significantly different between clopidogrel- and prasugrel-treated patients (odds ratio, 0.90; 95% confidence interval [CI], 0.80-1.02; p = 0.0949). The adjusted mean ± S.D. hospital LOS was 0.22 day lower (95% CI, 0.15-0.28; p < 0.001) with the use of prasugrel versus clopidogrel, and adjusted total mean hospital costs were $375 less for prasugrel-treated patients (p = 0.003). CONCLUSION: After adjustments for demographic and clinical characteristics, rates of inhospital bleeding in patients who received prasugrel and those who received clopidogrel were not significantly different. The adjusted analyses showed that the mean hospital LOS was shorter and total mean hospital costs were lower for patients treated with prasugrel.

"Real-World" Comparison of Prasugrel With Ticagrelor in Patients With Acute Coronary Syndrome Treated With Percutaneous Coronary Intervention in the United States.

OBJECTIVES: The 30-day clinical outcomes with prasugrel or ticagrelor were compared using a US payer database in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI). BACKGROUND: Prasugrel and ticagrelor demonstrated superior efficacy with increased non-coronary artery bypass graft major bleeding compared with clopidogrel in randomized clinical trials. No direct randomized or observational studies have compared clinical outcomes between prasugrel and ticagrelor. METHODS: Patients hospitalized for ACS-PCI between August 1, 2011 and April 30, 2013 and prescribed prasugrel or ticagrelor were selected. Drug treatment cohorts were propensity matched based upon demographic and clinical characteristics. The primary objective compared 30-day net adverse clinical events (NACE) in prasugrel- and ticagrelor-treated patients using a prespecified 20% noninferiority margin. Secondary objectives included comparisons of major adverse cardiovascular events (MACE) and major bleeding. RESULTS: Data were available for 16,098 patients (prasugrel, n = 13,134; ticagrelor, n = 2,964). In unmatched cohorts, prasugrel-treated patients were younger with fewer comorbidities than ticagrelor-treated patients, and 30-day NACE rates were 5.6 and 9.3%, respectively (P < 0.001). Following propensity matching, NACE was noninferior (P < 0.001) and 22% lower in prasugrel-treated than in ticagrelor-treated patients (RR, 0.78; 95% CI, 0.64-0.94). A 30-day adjusted MACE (RR, 0.80; 95% CI, 0.64-0.98) and major bleeding (RR, 0.65; 95% CI, 0.45-0.95) were also lower in prasugrel-treated patients compared with ticagrelor-treated patients. CONCLUSIONS: In this "real-world," retrospective, observational study, physicians appear to preferentially use prasugrel in younger patients with lower risk of bleeding or comorbidities compared with ticagrelor. Following adjustment, clinical outcomes associated with prasugrel use appear as good, if not better, than those associated with ticagrelor in ACS-PCI patients. © 2015 Wiley Periodicals, Inc.

Real-world observations with prasugrel compared to clopidogrel in acute coronary syndrome patients treated with percutaneous coronary intervention in the United States.

OBJECTIVES: To compare 30 and 90 day real-world acute myocardial infarction (AMI) and bleeding related rehospitalization rates in acute coronary syndrome (ACS) patients receiving percutaneous coronary intervention (PCI; ACS-PCI) treated with clopidogrel or prasugrel. RESEARCH DESIGN AND METHODS: Using the Premier hospital database, ACS-PCI patients receiving a drug-eluting (DES) or bare-metal (BMS) stent and clopidogrel or prasugrel from July 2009 to June 2011 were analyzed. Patients were included based on the prasugrel US prescribing information (USPI), excluding patients with a history of transient ischemic attack/stroke and patients ≥75 years without diabetes or prior MI. The primary endpoint was 30 day adjusted AMI rehospitalization rate. Secondary endpoints included 90 day AMI and 30 and 90 day bleeding-related rehospitalization rates. Treatment comparisons were adjusted using propensity score stratification. RESULTS: At the index event, prasugrel patients (N = 9404) differed from clopidogrel patients (N = 74,163) by having a lower risk of comorbid conditions associated with bleeding, being more likely younger and male, having ST-elevation MI and receiving a DES. For clopidogrel and prasugrel, respectively, the observed AMI-related rehospitalization rates were 4.7% and 3.9% at 30 days (p < 0.0001) and 6.3% and 5.1% at 90 days (p < 0.0001). After adjustment, prasugrel was associated with ∼10% lower odds of AMI-related rehospitalization (30 days: OR = 0.892 [95% CI: 0.798, 0.998]; 90 days, OR = 0.901 [95% CI: 0.817, 0.994]). Adjusted bleeding-related rehospitalization rates were similar to each other (OR = 1.035 at 30 days [95% CI: 0.765, 1.399]; OR = 0.922 at 90 days [95% CI: 0.725, 1.172]). STUDY LIMITATIONS: Treatment adherence was not assessed. Bleeding events not resulting in a hospitalization (e.g. office, outpatient, or emergency room visits), deaths outside the hospital, or readmissions to a hospital outside of the Premier alliance were not captured in the database. CONCLUSIONS: The different patient characteristics between prasugrel- and clopidogrel-treated patients suggest physicians are more selective in choosing patients for prasugrel than recommended in the prasugrel USPI. However, after adjustment for these differences, 30 and 90 day AMI rehospitalization rates were lower for prasugrel-treated patients compared to clopidogrel-treated patients, with no difference in adjusted bleeding-related rehospitalization rates.

A blood-based gene expression test for obstructive coronary artery disease tested in symptomatic nondiabetic patients referred for myocardial perfusion imaging the COMPASS study.

BACKGROUND- Obstructive coronary artery disease diagnosis in symptomatic patients often involves noninvasive testing before invasive coronary angiography. A blood-based gene expression score (GES) was previously validated in nondiabetic patients referred for invasive coronary angiography but not in symptomatic patients referred for myocardial perfusion imaging (MPI). METHODS AND RESULTS- This prospective, multicenter study obtained peripheral blood samples for GES before MPI in 537 consecutive patients. Patients with abnormal MPI usually underwent invasive coronary angiography; all others had research coronary computed tomographic angiography, with core laboratories defining coronary anatomy. A total of 431 patients completed GES, coronary imaging (invasive coronary angiography or computed tomographic angiography), and MPI. Mean age was 56±10 years (48% women). The prespecified primary end point was GES receiver-operating characteristics analysis to discriminate ≥50% stenosis (15% prevalence by core laboratory analysis). Area under the receiver-operating characteristics curve for GES was 0.79 (95% confidence interval, 0.73-0.84; P<0.001), with sensitivity, specificity, and negative predictive value of 89%, 52%, and 96%, respectively, at a prespecified threshold of ≤15 with 46% of patients below this score. The GES outperformed clinical factors by receiver-operating characteristics and reclassification analysis and showed significant correlation with maximum percent stenosis. Six-month follow-up on 97% of patients showed that 27 of 28 patients with adverse cardiovascular events or revascularization had GES >15. Site and core-laboratory MPI had areas under the curve of 0.59 and 0.63, respectively, significantly less than GES. CONCLUSIONS- GES has high sensitivity and negative predictive value for obstructive coronary artery disease. In this population clinically referred for MPI, the GES outperformed clinical factors and MPI. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT01117506.

Whole blood gene expression testing for coronary artery disease in nondiabetic patients: major adverse cardiovascular events and interventions in the PREDICT trial.

The majority of first-time angiography patients are without obstructive coronary artery disease (CAD). A blood gene expression score (GES) for obstructive CAD likelihood was validated in the PREDICT study, but its relation to major adverse cardiovascular events (MACE) and revascularization was not assessed. Patients (N = 1,160) were followed up for MACE and revascularization 1 year post-index angiography and GES, with 1,116 completing follow-up. The 30-day event rate was 23% and a further 2.2% at 12 months. The GES was associated with MACE/revascularizations (p < 0.001) and added to clinical risk scores. Patients with GES >15 trended towards increased >30 days MACE/revascularization likelihood (odds ratio = 2.59, 95% confidence interval = 0.89-9.14, p = 0.082). MACE incidence overall was 1.5% (17 of 1,116) and 3 of 17 patients had GES ≤ 15. For the total low GES group (N = 396), negative predictive value was 90% for MACE/revascularization and >99% for MACE alone, identifying a group of patients without obstructive CAD and highly unlikely to suffer MACE within 12 months.

Pharmacodynamics of a novel designer natriuretic peptide, CD-NP, in a first-in-human clinical trial in healthy subjects.

CD-NP is a novel chimeric natriuretic peptide (NP) consisting of the 22-amino-acid (AA) human C-type natriuretic peptide (CNP), a venodilating peptide with limited renal actions and minimal effects on blood pressure, and the 15-AA C-terminus of Dendroaspis NP (DNP). The rationale for the design of CD-NP was to enhance the renal actions of CNP, the ligand for natriuretic peptide receptor-B, but without inducing excessive hypotension. Here we report the first-in-human studies for CD-NP, which represent the first successful clinical testing of a chimeric NP demonstrating in normal human volunteers that CD-NP possesses cyclic guanosine monophosphate-activating, natriuretic, and aldosterone-suppressing properties without inducing excessive hypotension, laying the foundation for additional studies on this first-in-class new cardiovascular therapeutic in human heart failure, which are now underway worldwide.

The RegEx trial: a randomized, double-blind, placebo- and active-controlled pilot study combining regadenoson, a selective A(2A) adenosine agonist, with low-level exercise, in patients undergoing myocardial perfusion imaging.

BACKGROUND: Although vasodilator stress myocardial perfusion imaging (MPI) is increasingly performed with exercise, adenosine A(2A) receptor agonists have not been studied with exercise. OBJECTIVES: To determine the safety of administering regadenoson during exercise and, secondarily, to evaluate image quality, patient acceptance, and detection of perfusion defects. METHODS: Patients requiring pharmacologic MPI received a standard adenosine-supine protocol (AdenoSup, n = 60) and were then randomized (2:1) in a double-blind manner to low-level exercise with bolus intravenous injection of regadenoson (RegEx, n = 39) or placebo (PlcEx, n = 21). RESULTS: Adverse events occurred in 95%, 77%, and 33% of patients receiving AdenoSup, RegEx, and PlcEx, respectively. Peak heart rate was 13 beats per minute (bpm) and 21 bpm greater following RegEx compared to that following PlcEx and AdenoSup, respectively (P = .006 and <.001). Change from baseline in mean systolic blood pressure (SBP), change from baseline to nadir SBP, and percentage of patients with a decline in SBP by > or = 20 mm Hg showed no important differences between RegEx and PlcEx. No occurrences of 2nd degree or higher AV block were observed following RegEx or PlcEx; one patient developed 2nd degree AV block following AdenoSup. The mean heart-to-liver and heart-to-gut ratios were improved on RegEx vs AdenoSup: 0.85 (0.34) vs 0.65 (0.26), P < .001 and 1.1 (0.36) vs 0.97 (0.34), P < .001, respectively. Compared to AdenoSup, 70% of patients felt RegEx was much or somewhat better. CONCLUSIONS: Combining regadenoson with low-level exercise is feasible, well tolerated, and associated with fewer side effects compared to AdenoSup.

Safety of regadenoson, an adenosine A2A receptor agonist for myocardial perfusion imaging, in mild asthma and moderate asthma patients: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: Patients with reactive airways are at risk for adenosine-induced bronchoconstriction, mediated via A(2B) and/or A(3) adenosine receptors. METHODS AND RESULTS: To examine the effects of regadenoson, a selective adenosine A(2A) receptor agonist, on airway resistance, we conducted a randomized, double-blind, placebo-controlled crossover trial in asthmatic patients with a positive adenosine monophosphate challenge test. The mean ratio of the forced expiratory volume in 1 second (FEV(1)) at each tested time point relative to the baseline FEV(1) was significantly higher after treatment with regadenoson compared with placebo from 10 to 60 minutes after treatment. One patient had a substantial but asymptomatic FEV(1) reduction (-36.2%) after regadenoson that reversed spontaneously. The most common adverse events with regadenoson were tachycardia (66%), dizziness (53%), headache (45%), and dyspnea (34%). The mean heart rate significantly increased with regadenoson (maximum of +10.4 beats/min) versus placebo. CONCLUSIONS: In this pilot safety study of 48 patients with mild or moderate asthma who had bronchial reactivity to adenosine monophosphate, regadenoson was safe and well tolerated.

Regadenoson, a selective A2A adenosine receptor agonist, causes dose-dependent increases in coronary blood flow velocity in humans.

BACKGROUND: Regadenoson is a selective A2A adenosine receptor agonist and vasodilator used to increase the heterogeneity of distribution of coronary blood flow during myocardial perfusion imaging. This study characterized the dose dependence of regadenoson-induced coronary hyperemia. METHODS AND RESULTS: An open-label, dose-escalation study of regadenoson (10-500 microg, rapid intravenous bolus) was performed in 34 subjects; in 4 additional subjects, the effect of aminophylline to reverse the response to regadenoson was determined. Intracoronary peak blood flow velocity in either the left anterior descending or left circumflex artery was measured by continuous Doppler signal recording, heart rate, central aortic blood pressure, and adverse effects were recorded. Regadenoson increased peak blood flow velocity by up to 3.4-fold in a dose-dependent manner. The mean duration of the increase in flow velocity of 2.5-fold or greater caused by 400 to 500 microg of regadenoson was 2.3 to 2.4 minutes. Regadenoson (400-500 microg) increased heart rate by up to 21 +/- 6 beats/min and decreased systolic blood pressure (-5 +/- 8 mm Hg to -24 +/- 16 mm Hg) and diastolic blood pressure (-8 +/- 4 mm Hg to -15 +/- 14 mm Hg). Aminophylline (100 mg) attenuated the increase in peak flow velocity but not tachycardia caused by 400 microg of regadenoson. CONCLUSION: The results of this study demonstrate the utility of regadenoson as a coronary vasodilator for myocardial perfusion imaging.

On the physiological importance of endoproteolysis of CAAX proteins: heart-specific RCE1 knockout mice develop a lethal cardiomyopathy.

Proteins terminating with a CAAX motif, such as the Ras proteins and the nuclear lamins, undergo post-translational modification of a C-terminal cysteine with an isoprenyl lipid via a process called protein prenylation. After prenylation, the last three residues of CAAX proteins are clipped off by Rce1, an integral membrane endoprotease of the endoplasmic reticulum. Prenylation is crucial to the function of many CAAX proteins, but the physiologic significance of endoproteolytic processing has remained obscure. To address this issue, we used Cre/loxP recombination techniques to create mice lacking Rce1 in the heart, an organ where Rce1 is expressed at particularly high levels. The hearts from heart-specific Rce1 knockout mice manifested reduced levels of both the Rce1 mRNA and CAAX endoprotease activity, and the hearts manifested an accumulation of CAAX protein substrates. The heart-specific Rce1 knockout mice initially appeared healthy but died starting at 3-5 months of age. By 10 months of age, approximately 70% of the mice had died. Pathological studies revealed that the heart-specific Rce1 knockout mice had a dilated cardiomyopathy. By contrast, liver-specific Rce1 knockout mice appeared healthy, had normal transaminase levels, and had normal liver histology. These studies indicate that the endoproteolytic processing of CAAX proteins is essential for cardiac function but is less important for the liver.

Eliminating atherogenesis in mice by switching off hepatic lipoprotein secretion.

BACKGROUND: LDL receptor-deficient "apolipoprotein (apo)-B100-only" mice (Ldlr-/-Apob100/100 have elevated LDL cholesterol levels on a chow diet and develop severe aortic atherosclerosis. We hypothesized that both the hypercholesterolemia and the susceptibility to atherosclerosis could be eliminated by switching off hepatic lipoprotein production. METHODS AND RESULTS: We bred Ldlr-/-Apob100/100 mice that were homozygous for a conditional allele for Mttp (the gene for microsomal triglyceride transfer protein) and the inducible Mx1-Cre transgene. In these animals, which we called "Reversa mice," the hypercholesterolemia could be reversed, without modifying the diet or initiating a hypolipidemic drug, by the transient induction of Cre expression in the liver. After Cre induction, hepatic Mttp expression was virtually eliminated (as judged by quantitative real-time PCR), hepatic lipoprotein secretion was abolished (as judged by electron microscopy), and LDLs were virtually eliminated from the plasma. Intestinal lipoprotein production was unaffected. In mice fed a chow diet, Cre induction reduced plasma cholesterol levels from 233.9+/-46.0 to 37.2+/-6.5 mg/dL. In mice fed a high-fat diet, cholesterol levels fell from 525.7+/-32.2 to 100.6+/-14.3 mg/dL. The elimination of hepatic lipoprotein production completely prevented both the development of atherosclerosis and the changes in gene expression that accompany atherogenesis. CONCLUSIONS: We developed mice in which hypercholesterolemia can be reversed with a genetic switch. These mice will be useful for understanding gene-expression changes that accompany the reversal of hypercholesterolemia and atherosclerosis.